Magnetic sound-powered telephonic unit



Jan- 2, 1951 I l. HELLER 2,536,179

MAGNETIC SOUND-POWERED TELEPHONIC UNIT Filed April 5, 1950 2 Sheets-Sheet 1 Zgac 15 625421 Jan. 2, 1951 1. HELLER 2,536,179

MAGNETIC SOUND-POWERED TELEPHONIC UNIT Filed April 5, 1950 2 Sheets-Sheet 2 Patented Jan. 2, 1951 MAGNETIC SOUND-POWERED TELEPHONIC UNIT Isaac Heller, Brooklyn, N. Y., assignor to Remco Industries, Newark, N. J., a partnership Application April 5, 1950, Serial No. 154,180

Claims. (01. 179-108) system. The improved unit is especially designed for use in so-called walkie-talkie communication systems.

A prime object of the present invention is to provide a telephonic unit of this type that is simple and compact in construction light in weight and economical to manufacture yet has adequate power, sensitivity and fidelity charac teristics for entertainment, household and commercial purposes.

A further object of the invention is to provide a telephonic unit of this kind with improved means for establishing and securing the armature in position of maximum responsiveness to the inductive action of the coil and also to the action of the magnetic pole pieces.

Telephonic units of the general character described include a flexible armature leg that vibrates between magnetic pole pieces and the armature is connected by a driving rod or pin to a diaphragm; and another object of the invention is to provide novel and improved means for normally locating and holding said armature leg equidistantly spaced from said opposed pole pieces without the necessity of grinding the pole pieces to exact dimensions.

Other objects and advantages of the invention will be apparent from the description thereof to follow taken in connection with the accompanying drawings, in which Figure 1 is a perspective view of a fragment of the interior of a home showing a telephonic system having units embodying the present invention in use;

Figure 2 is a front elevational View of a box containing the improved unit;

Figure 3 is a side view thereof;

Figure 4 is a rear view thereof;

Figure 5 is a cross-sectional view taken on the plane of the line 5-5 of Figure 2;

Figure 6 is a cross-sectional view taken on the plane of the line 66 of Figure 3;

Figure '7 is a fragmentary vertical'sectional view taken through the box on a line to one side of the unit, parts being shown in section;

Figure 8 is a similar view taken on a line through the center of the unit on the plane 8--8 of Figure 6;

Figure 9 is a vertical sectional View taken on the plane of the line 9-9 of Figure 6;

Figure 10 is a vertical sectional view taken on the plane of the line Ill-40 of Figure 6;

Figure 11 is a vertical sectional view taken on the plane of the line Illl of Figure 6;

Figure 12 is a perspective view of a strip of magnetic material from which a magnet used with the improved unit is cut, and

Figure 13 is a perspective view of a magnet formed from the strip of Figure 12 and used with the improved unit. 4

The particular embodiment of the present invention is illustrated as contained in an elongated box I, rectangular in cross section, which may be formed of any suitable material. The box is of fairly small size, say six inches long, three.

inches wide and two inches deep, easy to handle and manipulate and this fact makes it practical to use the device in so-called walkie-talkie" communication systems. The boxhas a cover at each end, one of which may be removable to permit access to the interior for any desired purpose. The front wall 2 of the box may be painted or otherwise ornamented with instruments, such as scales, buttons and the like, in order to give the box a finished effect, as shown in Figure 2.

The diaphragm 3 is in the form of a cone of suitable metallic or other material with its rim extending through an opening in the front wall of the box and glued to the outer surface of the box around the edge of the opening. A combined mouth and ear piece 4, with the usual central opening, is suitably fastened by glue or otherwise on the outer wall of the box around the opening, covering the rim of the diaphragm.

The operating or driving assembly is supported on a suitable plate 5 secured to the inner surface of the rear wall 6 of the box by headed rivets 7. This assembly comprises a magnet 9, a motor unit comprising two pole pieces H], a field or energizing coil I l lying within the closure formed by the pole pieces and magnet, a vibratf ing armature [2, a pin [3 furnishing a driving connection between the armature and the cone, and a stabilizing or tensioning means l4.

The magnet 9 consists of a single rectangular bar of permanent magnetic material having a central groove I5 as shown in Figure 13. The bar may be cut from an elongated strip [6 of magnetic material, the strip being formed with spaced grooves l5 facilitating breaking off or cutting off 3 of magnets, such as the magnet 9. The strip I 6 is made of high residual flux density metal comprising an aluminum, nickel, steel alloy known to the trade as Alnico steel.

The pole pieces lil are formed of magnetic material such as steel or some other ferrous metal. Each pole piece is in the form of a plate, one end of which isangled to provide an offset portion ii". The pole pieces are arranged with their straight ends clamped to the ends of magnet 9 and with their ofiset ends IT in face-toface opposed relationship to provide a small clearance therebetween. A tubular rivet l8 passing through openings in the clamped ends of the pole pieces and through the groove 15 in the magnet secures said parts to the supporting plate 5.

The armature i2 comprises a sheet metal stamping of magnetic material having abase portion l9 with two projecting end legs 2!) and a projecting central leg 21 slightly longer than the end legs. The armature is positioned so that the edge of its base portion rests on: the surface of magnet a midway its ends. The end legs 26 extend between and are secured to the offset end portions" of the pole pieces by eyelets 22 througlr openings insaid legs and said offset end portions'at the corners ofsaid offset end portions, The legs 26 are magnetically insulated from the pole pieces by thin brass washers 23 on both sides, said washers spacing the end legs away from the pole pieces and providing an air gap 24 between the center portions of the pole pieces. The central leg 2| is free to vibrate "as a reed in the air gap and thislleg is pierced: to receive one end-of a diaphragm connector in theform: of thedriving pin 13, the other end of the pin being connected to the apex of the cone. The brass washers properly center the armature leg 21 in. the air gap so that its neutral position is equidistant from the pole pieces. 7

The armature stamping i2 is preferably made of magnetic material which is low in residual magnetism and is relatively thin. A suitable material for such an armature is an alloy including approximately 50% of nickel and 50% of iron.

The energizing coil H is of the self-supporting type and is telescoped over the armature leg 2! in the space provided by the pole pieces and magnet. The ends 25 and 26 of the coil wire are connected to the inner ends of the fastening eyelets I on the rear Wall 6. Spring terminal clips 21 are secured to the outer ends of the eyelets 2 for detachably and operatively connecting conductors 28 leading to a remote box E (Figure 1) for bringing said latter box with its unit in circuit.

In the assembly, the pole pieces are of opposite polarity so that the vibratory end of armature legZl lies in a strong magnetic field.

The presence of an oscillating current in the field coil furnishedby sound waves impinging against the diaphragm sets up corresponding electrical effects inthe armature which interact with the field between the pole pieces to cause the armature to rock back and. forth and drive the diaphragm 3- in mechanical oscillations which correspond substantially tothe current input.

The improved stabilizng or tensioning means it heretofore mentioned comprises a thin strip of flexible non-magnetic metal havin one end disc-shaped and rigidly fastened to one end of the tubular rivet i8 and insulated from the adjacent pole piece If] by a saucer-shaped plate or all) washer 29. The other end of strip [4 is fastened to the driving pin l3 by solder or the like so that it will vibrate with the pin. The presence of this strip It provides for maintaining the flexible armature leg 2| normally in equidistantly spaced relation to the offset portions 11 0f the magnetic pole pieces i0, as best shown in Figures 5 and 8. For example, in assembling the unit; after the driving pin i3 has been connected to the diaphragm and to the armature leg, said armature leg is positioned midway between the offset portions I? of the pole pieces and then th driving pin is soldered to the stabilizing arm M, whereafter said stabilizing arm will normally hold the armature leg in said position but will permit vibration of the armature leg by both sound waves impinging upon the diaphragm 3 and by the electromotive force induced in the coil i l.

structurally, it will be seen that the invention is simple, practical and inexpensive, the operation is direct, positive and powerful, and the boxcontainin the unit is particularly useful because of its supporting and housing characteristics for the unit and its accessories.

Changes in details of construction might be made and parts used without others without departing from the principle of the invention.

Having thus described the invention, what I claim is:

1. In a telephonic unit, pole pieces comprising plates of magnetic material each having one end portionoffset toward the correspondin end portion. of the other plate in spaced opposed relation thereto to form an. air gap between said ofiset portions, a permanent magnet clamped between the-other end portionsof said plates, an arma.-- turehaving a portion poised in said air gap, non-- magnetic clamping means fastening together and spacing said ofiset endportions with said armature clamped therebetween and said portion of the armature free to vibrate in' sa d gap; a field coil on said armature, a diaphragm, and a driving pin connecting said armature to said diaphragm, said armature being juxtaposed to saidpermanent magnet and having three spaced paral-lel legs the intermed ate one of which is poisedin said air gap while the other two are fastened between said pole pieces.

2. In a telephone unit, pole pieces comprising plates of magnetic material each having one end portion offset toward the corresponding end portion of the other plate in spaced opposed relation thereto to form an air gap between said offset portions, a permanent magnet clamped between the other end portions of said plates, an armature having a portion poised in. said air gap, non-magnetic clamping means fastening together and spacing said offset end portions with said armature clamped therebetweenand said portion of the armature free to vibrate in said gap, afield coil on said armature, a diaphragm, a. driving pin connecting said armature to said diaphragm, said armature being juxtaposed to said permanent magnet and having three spaced parallel legs the intermediate one of which is poised in said air gap while the other two are fastened between said pole pieces, and said non-magnetic clamping means comprising non-magnetic washers interposed between and spacing said offset end portions of said pole pieces and said armature legs, and non-magnetic fastening elements securing said end portions of the pole pieces together.

3. A- magnetic sound-powered telephonic unit comprising a permanent magnet, a pair of pole pieces formed as plates in clamping engagement with the ends of the magnet, each pole piece being Wholly of magnetic material and having offset end portions in face-to-face relationship with aligned openings, the straight ends of said pole pieces having alined openings, a sheet metal armature having end leg members and a central vibrating leg member extending between the offset end portions of the pole pieces, said end leg members having openings adjacent their ends in alinement with the openings in the offset end portions of the pole pieces, a brass eyelet extending between the aligned openings in the ofiset' end portions and in the end leg members for connecting the armature and said end portions together, brass washers on said eyelets for spacing the end leg members away from the pole pieces to establish an air gap between the centers of said pole pieces, an armature energizing coil surrounding the vibrating leg of said armature and being positioned between the pole pieces and a tubular rivet passing through the openings in the straight ends of said pole pieces to secure the parts together.

4. A magnetic sound-powered telephonic unit comprising a permanent magnet, a pair of complementary pole pieces, each being in the form of a one-piece plate of permanent magnet material and each including an offset end portion and being assembled with the offset end portions in opposed face-to-face relationship. said pole pieces being arranged with the plate portion of one piece contacting the north pole of the magnet and with the plate portion of the other piece contacting the south pole of the magnet, a flat sheet metal armature of magnetic material having two supporting legs fastened to the pole pieces between the offset ends and having a vibrating leg disposed between and extending beyond the gap between the central portions of the offset ends of the pole pieces, an armature energizing coil surrounding said vibrating leg, and washers ofnonrnagnetic material on each side of the supporting legs for establishing the spacing between said pole pieces. 5. A magnetic sound-powered telephonic unit comprising a support having an opening therein, a permanent magnet in the form of a bar having a central groove, a pair of complementary pole pieces, each being in the form of a one-piece plate of magnetic material and each having an offset end portion and being assembled with the offset end portions in opposed face-to-face relationship, said pole pieces being arranged with the straight end portion of one piece contacting the north pole of the magnet and with the straight end portion or the other piece contacting the south pole of the magnet, a fiat sheet metal armature of magnetic material having two end supporting legs fastened to the pole pieces between the offset ends and having a central vibrating leg disposed between and extending beyond the gap between the central portions of the c-iiset ends of the pole pieces, an armature energizing coil surrounding said vibrating leg, a diaphragm operatively connected to said vibrating leg, the straight end pieces of said pole pieces having aligned openings, and a tubular rivet extending through the aligned openings in said pole pieces, the groove in said permanent magnet and through the opening in said support for clamping the pole pieces to the ends of the magnet and for securing the unit to the support.

ISAAC HELLER.

REFERENCES CITED The following references are of record in the file of this patent:

, UNITED STATES PATENTS Number Name Date 1,746,039 Himmer Feb. 4, 1930 1,814,798 Guedon July 14, 1931 2,241,105 Woodrufi" et al May 6, 1941 2,511,114 Lavery June 13, 1950 

